JP2509373B2 - Reflow soldering method and device for printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electronic component with a lead wire having a low heat resistance temperature and an electronic component (hereinafter referred to as SMD) having a high heat resistance temperature such as a chip component or a flat package. The present invention relates to a reflow soldering method and an apparatus for allowing a mixed board to be soldered by a reflow soldering apparatus.

[Conventional technology]

Conventionally, a printed circuit board on which an SMD having a relatively high heat resistance temperature is mounted is soldered by a reflow soldering device in a high temperature atmosphere uniformly maintained at a temperature of 210 to 250 ° C.

Also, in the case of a mixed board with an SMD with a high heat resistance temperature and an electronic component with a lead wire with a low heat resistance temperature, mount the SMD on the printed board coated with solder paste and then solder with a reflow soldering device, Next, after mounting the electronic components with lead wires on the above-mentioned printed circuit board, applying flux and preheating, soldering with a jet type solder bath or a flow dip type solder layer, and further using Freon (Dupont Product name) Washed with liquid etc.

[Problems to be Solved by the Invention]

By the way, due to the diversification of surface mounting technology and the cost reduction of printed circuit boards, of the electronic components with lead wires, which have been used in the flow dip type solder bath and jet type solder bath up to now, Low-grade electronic components have not been soldered by reflow soldering equipment.

For this reason, in the reflow soldering equipment currently used, the heating chamber is made uniform at a temperature of 210 to 250 ° C, so soldering of electronic parts having lead wires with a low heat resistance of 120 ° C is possible. There is a problem that it is not suitable for doing.

In addition, in order to solder the electronic components with lead wires in a jet solder bath or a flow dip solder bath, a flux coating device, a preheating device and a cleaning device are required. (Company name) Liquid is used, so if a part of the vapor is discharged to the outside, the cleaning liquid is wasted, which not only increases the product cost but also deteriorates the working environment and causes pollution. There were problems such as becoming a friend.

The present invention has been made to solve the above-mentioned problems, and lowers the heat resistant temperature by providing a difference in heating temperature between the main surface and the back surface of a printed circuit board that runs under the reflow chamber. An object of the present invention is to provide a method and apparatus for reflow soldering a printed circuit board that enables electronic components to be soldered by a reflow soldering apparatus.

[Means for solving the problem]

The reflow soldering method of the printed circuit board according to the present invention is that the SMD is soldered on its main surface and the printed circuit board is inverted to apply the solder paste to the through hole for inserting the lead wire of the electronic component on the back surface of the printed circuit board. After that, it is turned over again and the lead wire of the electronic component is inserted into the through hole.Then, it is placed on the conveyor of the reflow soldering machine that has the preheating chamber and the reflow chamber in sequence. The substrates are continuously conveyed so as to be in close contact with each other, the upper side of the preheating chamber and the upper side of the reflow chamber are heated to a low temperature, and the lower side of the preheating chamber and the lower side of the reflow chamber are heated to a high temperature. By doing so, the solder paste on the back surface of the printed circuit board is melted and then solidified to solder the electronic component to the printed circuit board.

Also, the printed circuit board reflow soldering apparatus according to the present invention holds the upper side of the preheating chamber and the upper side of the reflow chamber at a low temperature, and holds the lower side of the preheating chamber and the lower side of the reflow chamber at a high temperature. In order to create a temperature difference and solder on the back side of the printed circuit board, it was heated at the lower side of the reflow chamber between each side wall of the preheating chamber and reflow chamber and the chain guide having the guide rails of each transport chain. A shield plate is provided to prevent the hot atmosphere from flowing upward.

Further, a radiant heater for heating the back surface of the printed circuit board is provided on the lower side of the preheating chamber and the lower side of the reflow chamber, and in the vicinity of the conveyed printed circuit board.

Further, a punched steel plate that prevents the radiant heat generated inside the upper portion of the reflow chamber from being absorbed by the printed circuit board is provided below the upper portion of the reflow chamber.

[Action]

In the present invention, the printed circuit board with the SMD soldered on the main surface of the printed circuit board is inverted, and the solder paste is applied to the through holes on the back surface of the printed circuit board. Insert the lead wire into the through hole, and then reflow solder the back surface of the printed circuit board.

Further, by providing a shielding plate between the preheating chamber, the side wall of the reflow chamber, and the chain guide having the guide rail of the transport chain, the thermal atmosphere on the lower side of the preheating chamber and the lower side of the reflow chamber becomes Entry into the upper side and the upper side of the reflow chamber is prevented.

Further, by providing the heater for heating the back surface of the printed circuit board, only the back surface of the printed circuit board is easily heated, and by providing the punched steel plate, the main surface of the printed circuit board is kept at a low temperature.

〔Example〕

1 (a) to 1 (c) show an embodiment of the present invention. FIG. 1 (a) is a side sectional view of the same, and FIG. 1 (b) is
Sectional drawing by the line I-I of FIG. 1 (a), FIG. 1 (c)
Is a sectional view taken along line II-II of FIG. 1 (a), FIG. 1 (d) is a side sectional view showing an enlarged portion of the shielding plate of FIG. 1 (c), and FIG. a) to (c) and FIG. 3 show the shape of the printed circuit board of FIG. 1 (a), FIG. 2 (a) to (c) are perspective views, and FIG. 3 is FIG. It is a sectional side view which shows the principal part of (c). In these figures, 1 is a printed circuit board, 2 is a chip component having a high heat resistant temperature, 3 is a solder paste, and in FIGS. 2 and 3, 4 is a flat package having a high heat resistant temperature, 5 is a printed circuit, and 6 is the above-mentioned. Through holes formed in the printed circuit board 1, 7 is an electronic component having a lead wire described later, and 8 is a lead wire of the electronic component 7 inserted into the through hole 6. 1a is the chip component
2, a main surface on the front side on which the flat package 4 and the electronic component 7 are mounted, and 1b is a back surface which is a back surface side of the main surface 1a.

Further, in FIGS. 1 (a) and 1 (b), reference numeral 11 denotes a transport chain among the transport conveyors for transporting the printed circuit board 1 as an example. Reference numeral 12 is a sprocket. In FIG. 1 (d), 13 is a holding claw, and 14 is the transfer chain 11.
Guide rails, 15 is a chain cover. In FIGS. 1 (a) to (c), reference numeral 21 denotes the entire reflow soldering apparatus. Reference numerals 22 and 23 denote a primary preheating chamber and a secondary preheating chamber that heat the printed circuit board 1 with air heated to a temperature lower than the melting point of the solder paste 3, and the traveling direction of the printed circuit board 1 (direction of arrow A). , Which are provided at the rear and the front of the, 22A, 23A is the upper side of the preheating chamber 22,23,
22B and 23B are lower sides of the preheating chambers 22 and 23, 24 is a reflow chamber for soldering the printed circuit board 1, 24A is an upper side of the reflow chamber 24, and 24B is a lower side of the reflow chamber 24. , 22a is a side wall of the primary preheating chamber 22, 23a is a side wall of the secondary preheating chamber 23, and 24a is a side wall of the reflow chamber 24. A heater 25 is attached to each side wall 22a, 23a, 24a formed in parallel with the traveling direction of the printed circuit board 1 (direction of arrow A) and heats air. A sheath heater, a far infrared heater or the like is used. Reference numeral 26 is a shield plate for shielding the radiation heat including the far infrared rays generated from the heater 25 from being radiated into the preheating chambers 22 and 23 and the reflow chamber 24. This is to prevent 2 from being heated. 27 is the shielding plate
The heating portion formed by 26. 28 is a blower fan that circulates the heated air, and a multi-blade blower or the like is used. 29 is a motor of each of the blower fans 28, 30 is an outlet for discharging heated air for melting the solder paste 3, 31 is an inlet formed below the heating unit 27, and 32 is each of the spares. Heating chambers 22,23, reflow chamber 24
A rectifying plate formed at the discharge port 30 of the air rectifies the turbulent air by the blower fan 28. 33 is a cooling fan, 34
Is an exhaust fan, and 35 is a flow passage of air from the heating unit 27 to the inside of the blower fan 28. 36 is the printed circuit board 1
It is a radiant heater that heats the back surface 1b of the above, and is provided below the transport chain 11. 37 is the chain cover 15 and each side wall
22a, 23a, 24a is a shielding plate that blocks the reflow chamber 24
It prevents the hot air heated in the lower side 24B from flowing upward. Reference numeral 38 denotes a punched steel plate provided below the upper side 24A of the reflow chamber 24, which is shown by broken lines in FIGS. 1 (a) and 1 (c), and has a large number of through holes not shown.

In FIG. 1, the upper side 2 of each preheating chamber 23, 24
2A, 23A, the lower side 22B, 23B and the upper side 24A, the lower side 24B of the reflow chamber 24 are provided vertically symmetrical with respect to the transport chain 11.

 Next, the operation will be described.

4 (a) to 4 (c) are diagrams showing a process of soldering the printed board 1. FIG.

First, as shown in FIG. 2 (a), FIG. 4 (a)
The chip component 2 is soldered to the upper main surface 1a of the printed circuit board 1.

Next, as shown in FIG. 4B, the printed circuit board 1 is turned over so that the main surface 1a is on the lower side and the back surface 1b is on the upper side, as shown in FIG. The solder paste 3 is applied to the portion of the through hole 6 into which the wire 8 is inserted. The solder paste 3 is applied by an injector or by covering the printed circuit board 1 with a plate-shaped screen having the same through holes as the printed circuit board 1 only on the through holes 6.

Next, as shown in FIG. 4 (c), as shown in FIG. 2 (c), the printed circuit board 1 is turned over again so that the main surface 1a is on the upper side and the back surface 1b is on the lower side. 8 is passed through the through hole 6 and the reflow soldering device 21 shown in FIG.
Transport to

Next, in the reflow soldering device 21, each preheating chamber
The upper sides 22A and 23A of 22,23 hold the solder paste 3 soldered by a reflow soldering device (not shown) in the preceding stage in an atmosphere of a temperature of about 130 ° C. that does not melt again. The temperatures of the lower sides 22B, 23B of the preheating chambers 22, 23 are kept higher than those of the upper sides 22A, 23A. Also, the upper side 24A of the reflow chamber 24
The inside is kept in an atmosphere at a temperature of about 100 ° C. Further, by providing the punched steel plate 38, the low-temperature hot air in the upper portion has a high flow velocity when passing through the through holes of the punched steel plate 3, so that the low-temperature hot air can be blown to the main surface 1a of the printed board 1. At the same time, it prevents near infrared rays from being absorbed by the main surface 1a. The stamped steel plate 38 may be provided in each of the preheating chambers 22 and 23. In this case, it is suitable when using an electronic component with a lead wire having a higher temperature than usual.

Further, the inside of the lower side 24B of the reflow chamber 24 is heated to a temperature of about 400 ° C. by hot air and near infrared rays generated from the radiant heater 36.

By providing the shield plate 37, the hot atmosphere such as hot air or radiant heat in the lower side 24B of the reflow chamber 24 is changed to the upper side 22A, 23A of each preheating chamber 22, 23 and the upper side 24 of the reflow chamber 24.
It prevents it from flowing into A.

Next, in order to solder the lead wire 8 of the electronic component 7 mounted on the printed circuit board 1, the printed circuit board 1 is mounted on the holding claws 13 of the carrier chain 11 as shown in FIG. It is preheated through the preheating chambers 22 and 23 of the soldering device 21, and then the lower side 24 of the reflow chamber 24.
Soldered at B.

In the reflow chamber 24, the main surface 1a of the printed circuit board 1 has a temperature of about 100 ° C. in the upper side 24A of the reflow chamber 24, and the punched steel plate 38 prevents the influence of near infrared rays. Low temperature is maintained.

In the lower side 24B of the reflow chamber 24, the solder paste 3 is heated by the hot air of about 400 ° C. and the near infrared rays from the radiant heater 36.
Are melted and soldered, and then cooled and fixed by the cooling fan 33.

Further, when soldering is performed by the reflow soldering device 21, the hot air from the lower side 24B of the reflow chamber 24 is discharged from between the transfer chains 11 to the upper side 22A, 23A of each preheating chamber 22, 23 and the reflow chamber 24. Even when the printed circuit board 1 is not mounted on the transport chain 11 in order to prevent it from flowing to the upper side 24A, the cover plate 41 is continuously spaced from the transport chain 11 as shown in FIGS. 5 (a) and 5 (b). Attach and transport as long as possible. Of course, in the case of the printed circuit board 1 as well,
The sheet is conveyed as shown in FIGS. further,
After the initial printed circuit board 1 is mounted, if a gap occurs in the mounting of the next printed circuit board 1, the cover plate 41 is continuously mounted until the next printed circuit board 1 is mounted.

FIG. 6 is a side sectional view showing another shape of the shielding plate 37 shown in FIG. 1 (d), and the shielding plate can be adjusted when the transport chain 11 is moved in accordance with the width of the printed board 1. It is made possible, 39 is a fixed side shield plate fixed to the side wall 24a, 40 is a movable side shield plate fixed to the chain cover 15, 39a, 40a of each of the shield plate 39, 40 L at the engaging part
It is formed into a shape.

7 (a) and 7 (b) are a plan view and a side sectional view showing another shape of the cover plate 41 of FIG. 5, in which the printed circuit board 1 has a small size and the width of the transport chain 11 is small. When the adjustment cannot be dealt with, or when the printed circuit board 1 cannot be continuously conveyed, a through hole 42 corresponding to the printed circuit board 1 is formed in the cover plate 41, and the printed circuit board 1 is placed on the through hole 42. To do.

FIGS. 8 (a) and 8 (b) show an embodiment in which a printed circuit board with a chassis is used. FIG. 8 (a) is a plan view and FIG. 8 (b) is FIG. 8 (a). 3) is a cross-sectional view taken along line III-III in FIG. In these figures, the same reference numerals as those in FIGS. 1 to 7 denote the same parts, and 51 denotes the printed circuit board 1.
Chassis made of magnetic material fixed to
A partition plate made of a magnetic material formed on 51, 53 lead wires protruding outward from the chassis 51, 54 a transport chain,
55 is a rod integrally attached to the transport chain 54, 56 is a magnet chuck attached to the rod 55, and the upper surfaces of the chassis 51 and the partition plate 52 are permanent magnets 57.
It is retained by being adsorbed by.

In this way, the chassis 51 to which the printed circuit board 1 is fixed
Is adsorbed and held by the magnet chuck 55, and the chip component 2 is soldered to the main surface 1a and the back surface 1b of the printed board 1 by a reflow soldering device (not shown), and then, FIGS. After inserting the lead wire 8 of the electronic component 7 into the through hole 6 of the printed board 1 and applying the solder paste 3 in the same process as the above, the chassis 51 corresponds to the through hole 42 of the lid plate 41 shown in FIG. Then, the reflow soldering device 21 shown in FIG. 1 is used for soldering.

〔The invention's effect〕

As described above, the reflow soldering method of the printed circuit board of the present invention is to reverse the printed circuit board having the SMD soldered on its main surface to form the through holes for inserting the electronic components and the lead wires on the back surface of the printed circuit board. After applying the solder paste, invert it again to insert the lead wire of the electronic component into the through hole, and then print the previous stage of the printed circuit board on the conveyor of the reflow soldering device that has the preheating chamber and reflow chamber in sequence. The substrate and the printed circuit board in the subsequent stage are continuously conveyed so as to be in close contact, and the upper side of the preheating chamber and the upper side of the reflow chamber are heated to a low temperature, and the lower side of the preheating chamber and the lower side of the reflow chamber are heated. The solder paste on the back side of the printed circuit board is melted by heating it to a high temperature and then solidified to solder the electronic components to the printed circuit board. Since it is possible to solder the lead parts of electronic parts by the reflow soldering method, there is no need for a flux applicator and a cleaning device after flux is applied, and therefore the Freon liquid cleaning liquid is not used. Therefore, there is an advantage that there is no pollution due to the discharge of the Freon liquid vapor and the manufacturing cost of the printed circuit board can be reduced.

The printed circuit board reflow soldering apparatus of the present invention holds the upper side of the preheating chamber and the upper side of the reflow chamber at a low temperature, and holds the lower side of the preheating chamber and the lower side of the reflow chamber at a high temperature. A thermal atmosphere in which the lower side of the reflow chamber is heated between the preheating chamber and each side wall of the reflow chamber and the chain guides that have the guide rails of each transport chain in order to make a temperature difference and to solder the back surface of the printed circuit board. Is provided with a shield plate for preventing upward flow, and a heater for heating the back surface of the printed circuit board is provided on the lower side of the preheating chamber and the lower side of the reflow chamber, and in the vicinity of the printed circuit board to be transported. Since a punched steel plate that prevents radiant heat generated inside the upper part of the reflow chamber from being absorbed by the printed circuit board is provided below the upper part of the reflow chamber,
Since only the back side of the printed circuit board is easily heated by the reflow soldering device and reflow soldering can be performed, the main surface of the printed circuit board can be reflow soldered even if the lead wire part of the electronic component with low heat resistant temperature lead wire is reflow soldered. Since it is kept at a low temperature, it has an advantage that electronic components can be prevented from being damaged by heat.

[Brief description of drawings]

1 (a) to 1 (c) show an embodiment of the present invention. FIG. 1 (a) is a side sectional view, and FIG. 1 (b) is I- of FIG. 1 (a). A cross-sectional view taken along the line I, FIG.
FIG. 1A is a sectional view taken along line II-II, FIG. 1D is an enlarged side sectional view showing a portion of the shielding plate of FIG. 1C,
2 (a) to (c) and FIG. 3 show the shape of the printed circuit board of FIG. 1 (a), and FIGS. 2 (a) to (c) are perspective views, and FIG. 2 (c) is a side sectional view showing an essential part, FIGS. 4 (a) to 4 (c) are views showing a process of soldering a printed circuit board, and FIGS. 5 (a) and 5 (b) are lids. FIG. 6 is a side view showing another shape of the second shield plate of FIG. 1 (d), FIG. (B) is shown in FIG.
FIG. 8B is a plan view and a side sectional view showing another shape of the cover plate of FIG. 8B, and FIGS. 8A and 8B show an embodiment in which a printed board with a chassis is used. 8A is a plan view, and FIG. 8B is a sectional view taken along line III-III in FIG. 8A. In the figure, 1 is a printed circuit board, 1a is a main surface, 1b is a back surface, 2 is a chip component, 3 is a solder paste, 6 is a through hole, 7 is an electronic component, 8 is a lead wire, 11 is a carrier chain, and 14 is a guide. Rail, 15 chain cover, 21 reflow soldering device, 22 primary preheating chamber, 23 secondary preheating chamber, 22A, 23
A is an upper side, 22B and 23B are lower sides, 24 is a reflow chamber, 24A is an upper side, 24B is a lower side, 22a, 23a and 24a are side walls, and 37 is a shielding plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-2-99266 (JP, A) JP-A-1-27794 (JP, A)

Claims (4)

(57) [Claims] 1. A printed circuit board having surface-mounted components soldered on its main surface is inverted, solder paste is applied to the through holes for inserting lead wires of electronic components on the back surface of the printed circuit board, and then inverted again. Insert the lead wire of the electronic component into the through hole, and then, on the transfer conveyor of the reflow soldering device in which the preheating chamber and the reflow chamber are sequentially provided, the printed circuit board in the front stage and the printed circuit board in the rear stage. Are continuously conveyed so as to be in close contact with each other, the upper side of the preheating chamber and the upper side of the reflow chamber are heated to a low temperature, and the lower side of the preheating chamber and the lower side of the reflow chamber are heated to a high temperature. By melting the solder paste on the back surface of the printed board by solidifying the solder paste, the electronic component is soldered to the printed board. Reflow soldering method. 2. A solder paste is applied to a through hole on a back surface of a printed circuit board having a surface mounting component soldered on its main surface, and a lead wire of an electronic component is inserted into the through hole from the main surface of the printed circuit board. And a reflow chamber for melting and soldering the solder paste, and a pre-heating chamber for heating the printed circuit board, and a pre-heating chamber for vertically heating the printed circuit board that is temporarily attached by a transfer conveyor. A reflow soldering device provided symmetrically, wherein the upper side of the preheating chamber and the upper side of the reflow chamber are kept at a low temperature, and the lower side of the preheating chamber and the lower side of the reflow chamber are kept at a high temperature. In order to make a temperature difference and solder the back surface of the printed circuit board, each side wall of the preheating chamber and the reflow chamber and the guide rail of each transport chain are provided. The reflow chamber PCB reflow soldering apparatus, characterized in that heated heat atmosphere lower side is provided with a shielding plate to prevent flow upward between the Engaido. 3. A radiant heater for heating the back surface of the printed circuit board is provided on the lower side of the preheating chamber and the lower side of the reflow chamber, and in the vicinity of the conveyed printed circuit board. A printed circuit board reflow soldering apparatus as described above. 4. A punched steel plate for preventing the radiant heat inside the upper part of the reflow chamber from being absorbed by the printed circuit board is provided below the upper part of the reflow chamber. ) The reflow soldering device for a printed circuit board according to [1].